"We are deeply saddened to learn of this tragic incident and offer our condolences to the Ma family," Apple said in a statement issued to the Xinhua news agency. "We will fully investigate and co-operate with authorities in this matter."

A similar incident occurred in China in 2010 when a man using his mobile phone with an unauthorised charger was fatally electrocuted.

However, Ms Ma is believed to have been using an iPhone 5 with its original charger at the time of her death.